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On inverse source problem for piecewise constant case
No full textWe consider inverse source problem at fixed positive frequency. We prove a global uniqueness theorem for this problem for the case of piecewise constant source
Femtosecond-laser-delamination cavities for resonant acousto-magneto-plasmonics
No full textInternational audienceFemtosecond lasers are routinely used for inducing local modification, including nanostructuring, and ultrafast laser spectroscopy in solids. However, these studies are often being performed separately making the unveiling of exciting physical properties of laser-fabricated materials out of reach. Here, we present an all-optical platform combining the fabrication of nano to micrometer size single-shot “femtosecond-laserdelamination” membranes or cavities of ferromagnetic thin films and multilayers together with their quasi in situ characterization using the Abbe-limited interferometric, ultrafast scanning photo-acoustic and magneto-plasmonic microscopies. Ferromagnetic nickel and iron cavities display high-Q acoustic resonances providing access to long-lived ultrahigh frequency coherent phonon modes in the above 100 GHz frequency range. Cavities in cobalt-gold bilayers allow for magnetically controlled surface plasmon resonance experiments in the Otto configuration, which is otherwise very difficult to implement experimentally. Quantitative experimental characterization of functional magnetic cavities, supported by the numerical modeling of all experimental data, opens an avenue to design and fabricate tunable nanoscaled femtosecond-laser-delamination architectures in thin films and multilayers
Synthèse, caractérisation et réactivité de complexes d'élément f avec des ligands aromatique hydrocarboné
No full textThis work focuses on various aspectsof the organometallic chemistry of f-elements.First is the synthesis of a new family oflanthanides involving the nine-membered ringligand cyclononatetraenyl (Cnt). Thesecomplexes were studied using variousspectroscopic methods.A difference in reactivity was observeddepending on the metal and the conformation ofthe ligand used (cis or trans). Next, theisomerization of the Cnt ligand and thelanthanide complexes containing this ligandwere studied. This study resulted in thesynthesis of a new family of complexes with thetrans-configured ligand and demonstrated theeffect of light on the isomerization of the ligandand these complexes.Additionally, a study on uranium was conductedusing the five-membered ligand 1,2,4-tri(tert-butyl)cyclopentadienyl, also known as Cpttt. TheUIII(Cpttt)2I complex was produced using a newsynthesis route that differs from those describedin the literature. Reducing this complex undervarious conditions demonstrated its ability toactivate diazote and break the N-N triple bond.This reactivity enabled us to hydrogenate andprotonate nitrogen atoms, forming ammoniumchlorides, molecules derived from ammonia.Finally, we decided to change the ligand andenlarge the cycle to ten members: 1,6-methano[10]annulene, also known as C10.Lanthanide complexes could be synthesizedwith this new ligand.Ce travail s’intéresse à différents aspects de la chimie organométallique des élément f. Dans un premier temps, la synthèse d’une nouvelle famille de lanthanide impliquant le ligand à neuf chainons, le cyclononatetraenyl (Cnt). Ces complexes ont été étudiés par divers moyens spectroscopiques. Par ailleurs, une différence de réactivité à été observée en fonction du métal utilisé mais aussi de la conformation du ligand utilisé : cis ou trans.Cette observation s’en est suivi d’une étude d’isomérisation du ligand Cnt ainsi que des complexes de lanthanide contenant ce ligand.Cette étude a permis de synthétiser une nouvelle famille de complexe avec le ligand en conformation trans et a montré l’impact de la lumière sur l’isomérisation du ligand et de ces complexes.Par ailleurs, une étude sur l’uranium a été menée en utilisant un ligand à cinq chainons, le 1,2,4-tri(tert-butyl) cyclopentadienyl ou Cpttt. Le complexe UIII (Cpttt) 2I a été réalisé en développant une nouvelle voie de synthèse que celle décrite dans la littérature. La réduction de ce complexe sous diverses conditions a montrés a capacité à non seulement activer le diazote mais aussi à casser la triple liaison N-N. Cette réactivité nous a permis d’hydrogéner et de protoner les azotes et ainsi de former des chlorures d’ammonium, molécule dérivée de l’ammoniaque. Enfin, il a ensuite été décidé de changer de ligand et d’agrandir le cycle à 10chainons : le 1,6-methano[10]annulène ou C10. Il a été possible de synthétiser des complexes de lanthanide avec ce nouveau ligand
The multi-dimensional environmental impact of global crop commodities
No full textInternational audienceAbstract Agriculture is one of the leading causes of detrimental environmental impacts, including greenhouse gas emissions, biodiversity loss and depletion of freshwater resources. Such impacts can be assessed by environmental sustainability indices; however, limitations in current indicators necessitate the development of more robust and standardized crop-specific environmental sustainability indices. Here we developed the crop environmental sustainability index (PLANTdex), a spatially explicit index (5 arcmin resolution) quantifying crop production’s environmental impacts. PLANTdex includes globally standardized indicators of environmental impacts assessing water stress and biodiversity loss via five emissions pathways: greenhouse gas emissions, water consumption, land occupation, and nitrogen and phosphorus fertilizer application. We applied PLANTdex to 16 crops, revealing high variability across production system efficiencies, crop types and local context environmental sensitivities. Globally and nationally, no clear correlation emerged between PLANTdex scores and crop production, but stronger correlations were evident at finer spatial scales and for individual crops. Sugar cane showed the strongest negative correlation (low impacts in high-production areas), while oil palm had the strongest positive correlation (high impacts in high-production areas), highlighting the importance of sub-national, crop-specific assessments. PLANTdex’s spatial resolution and crop specificity make it valuable for initiatives such as the Taskforce on Nature-related Financial Disclosures and corporate sustainability strategies
Transport of spherical microparticles in a 3D vortex flow
No full textParticles are common in biological and environmental flows and are widely used in industrial and pharmaceutical applications. Their motion and flow dynamics are strongly affected by interactions with the surrounding flow structure. While particle-flow interactions have been extensively studied in low Reynolds number (Re) flows as well as in fully developed turbulence, the transport mechanisms of these particles in intermediate flow regimes remain less explored. Here, we investigate the response of neutrally buoyant spherical particles to a single vortex flow field. Using a microfluidic crossslot geometry, we generate a well-characterized, stationary, three-dimensional streamwise vortex at moderate Re (∼ 50). Our experimental results, supported by numerical simulations, show that with increasing particle diameter, they are progressively excluded from the vortex core. Initially, small particles follow a Burgers vortex-like self-similar motion, but for larger particle diameters, deviations from this trend emerge due to fluid inertia and finite-size effects. These findings enhance our understanding of particle dynamics in vortical flows and have implications for microfluidic applications involving particle sorting and separation
Deubiquitinating enzyme UCH-L1 regulates neuronal Ca2+ signalling
No full textInternational audienceUbiquitination influences a myriad of biological processes like the trafficking or degradation of ubiquitin-tagged target proteins. This post-translational modification can be reversed by deubiquitinating enzymes (DUBs) that counterbalance the action of E3 ubiquitin ligases. We investigated the impact of PR-619, a membrane-permeable and broad-spectrum DUBs inhibitor, on the entry of Ca 2+ through native voltage-gated Ca 2+ channels (VGCCs) of cultured embryonic cortical neurons. Fura-2-based Ca 2+ imaging experiments showed that PR-619 reduced the cytosolic Ca 2+ rises induced by depolarization by affecting mainly dihydropyridine-sensitive (L-type) VGCCs. This inhibition was sensitive to the dynamin inhibitor Myr-Dip and the lysosomal agents chloroquine and bafilomycin-A. PR-619 also reduced the amount of Ca v 1.2 proteins. A pharmacological approach was set out to better delineate the identity of the DUB responsible of this inhibitory action of PR-619.Since UCH-L1 and USP19 are two highly expressed neuronal DUBs, we investigated the effects of selective UCH-L1 (IMP1710, GK13S) and USP19 (ADC141) inhibitors. IMP1710 and GK13S depressed the Ca 2+ uptake through L-type VGCCs whereas ADC141 and the UCH-L3 inhibitor TCID had no effects. In addition, UCH-L1 inhibition impaired the neuronal Ca 2+ storage capacities of neurons and reduced Cav1.2 protein levels. Thus, UCH-L1 influences the neuronal uptake and storage of Ca 2+ , which is likely to have important physiological implications. Altogether, these results posit UCH-L1, the main DUB of the brain, as an important regulator of the neuronal Ca 2+ homeostasis and add to our understanding of its cellular functions
Study of the molybdenum solid-plasma transition by femtosecond x-ray absorption near-edge spectroscopy
No full textInternational audienceWarm dense molybdenum produced by femtosecond laser heating is investigated using femtosecond time-resolved X-ray Absorption Near Edge Spectroscopy (XANES) near the Mo L 3 -edge (2.52 keV). Laser absorption and X-ray absorption measurements are performed, respectively to constrain hydrodynamic macroscopic simulations, and to obtain atomic-scale information on the dynamics of electron and ion structures. Ab initio calculations are performed to interpret XANES spectra. Preliminary results indicate an extremely rapid loss of the crystalline order (100 fs-scale), accompanied by a modification of the 4d-band electronic structure. This paper highlights the impact of the sample surface quality on the data analysis and interpretation
Tests of restricted Quantum Focusing and a new CFT bound
No full textInternational audienceThe restricted quantum focusing conjecture (rQFC) plays a central role in an axiomatic formulation of semiclassical gravity. Since much hinges on its validity, it is imperative to subject the rQFC to rigorous tests in novel settings. Here we do so in two independent directions. First, we prove rQFC in a class of spacetime dimension toy models, JT gravity coupled to a QFT. We also construct explicit counter-examples to the original and stronger Quantum Focusing Conjecture in a regime where matter quantum effects are comparable to the total dilaton value. Second, for , we derive from the rQFC a constraint stronger than the Quantum Null Energy Condition (QNEC). In a broad class of states, this bound forbids the QNEC from saturating faster than as the transverse area of a certain null deformation shrinks to zero. We speculate about a universal strengthened QNEC holding across all QFT states
The Davenport constant of balls and boxes
No full text43 pages, 4 figuresGiven an additively written abelian group and a set , we let denote the Davenport constant of , namely the largest non-negative integer for which there exists a sequence of elements of such that and for each non-empty proper subset of . In this paper, we mainly investigate the case when is and , and is a discrete Euclidean ball. An application to the classical problem of estimating the Davenport constant of a box - a product of intervals of integers - is then obtained
Analyse par tomographie aux rayons X de l’endommagement du sel gemme polycristallin synthétique : effet de la pression de confinement, de la présence de saumure et de la vitesse de déformation
No full textGreen hydrogen, produced from renewable energysources, is considered as a promising energy vector. Its large-scale storage in deep salt caverns is a potential solution toface the time gap between the energy production and its use.Indeed, rock salt is a rock with low porosity, low permeabi-lity and is inert to hydrogen. Salt caverns have already beenin use for seasonal storage of hydrocarbons. However, theintermittency of renewable energy sources means that injec-tion/withdrawal cycles have to be more frequent. Previous stu-dies have highlighted the coexistence of intra-crystalline andinter-crystalline deformation mechanisms, leading to micro-cracking of the material from the early stages of the plasticdeformation. The aim of the present work is to extend theseanalyses to triaxial loading conditions, which are more repre-sentative of the operating conditions in salt caverns, with anobservation of the evolution of porosity and micro-cracking in-side the samples. The study is performed on synthetic ma-terial with controlled microstructure, in which the grain sizeis suited to in situ mechanical testing means. Samples withdifferent brine contents can be produced with the elaborationprocesses using NaCl powder pressing that have been im-plemented. This enables the study of the effect of humidityon the activation of damage micro-mechanisms. The micro-structure of the obtained material is characterised with opticaland electronic microscopy and with EBSD. An in situ triaxialmachine, that has been modified for the needs of the study,allows us to observe the development of micro-cracks at dif-ferent confining pressures using laboratory and synchrotronX-Ray computed micro-tomography at a high imaging resolu-tion. The high flux of the synchrotron radiation enables shor-ter scan durations compared to the ones in laboratory, so thatseveral combination of confining pressures and loading ratescould have been tested on dry and wet samples. Under thetesting conditions considered, the viscoplastic deformation ofsalt is accompanied by diffuse grain boundary micro-cracking,indicating that mechanisms at the interfaces of grains are ne-cessary mechanisms to accommodate the local plastic incom-patibilities between neighbouring grains, even under signifi-cant confinements, representative of the lithostatic pressureof many salt caverns. An increase of the confinement andthe presence of brine seem to reduce the development of themicro-crack network. This suggests that dissolution precipita-tion mechanisms could be active and serve as local accom-modation mechanisms or operate as healing mechanisms.Dans un contexte de transition énergétique, le stockage dans des cavités salines profondes d’hydrogène vert est une solution envisagée pour faire face au déphasage entre production et consommation d’énergie. En effet, le sel gemme est une roche peu poreuse, imperméable et inerte vis-à-vis de l’hydrogène. L’intermittence des énergies renouvelables implique néanmoins des cycles d’injection et de sou-tirage plus fréquents comparés à ceux en usage pour un stockage saisonnier et donc de nouveaux modes de sollicitation. Des études antérieures ont montré la coexistence de mécanismes de déformation intra et inter cristallins, induisant la micro fissuration du matériau dès les premiers stades de la déformation plastique. Le présent travail vise à étendre ces analyses à des sollicitations triaxiales plus représentatives des conditions d’opération des cavités de stockage, avec une observation des évolutions de la porosité et de la microfissuration à cœur des échantillons. L’étude est menée sur des matériaux synthétiques de microstructure contrôlée,dont la taille de grains est adaptée aux moyens d’essais mécaniques in situ. Les procédés de fabrication par pressage de poudre de NaCl mis en place permettent d’élaborer des échantillons avec différentes teneurs en saumure, permettant ainsi l’analyse de l’effet de l’humidité sur l’activation des micro-mécanismes d’endommagement. Leur microstructure est caractérise en microscopie optique, électronique et par EBSD. Une machine d’essai triaxial in situ modifiée pour les besoins de l’étude permet d’observer le développement de microfissures par tomographie aux rayons X de laboratoire et sous faisceau synchrotron, où les temps d’imageries sont beaucoup plus courts grâce au flux important disponible.Ainsi, plusieurs combinaisons de pressions de confinement de vitesses de chargement ont pu être imposées à des échantillons de type sec et de type humide. Aux conditions d’essais considérées, la déformation viscoplastique du sel s’accompagne de microfissuration inter-granulaire diffuse, indiquant que les mécanismes aux joints de grains sont des mécanismes nécessaires à l’accommodation des incompatibilités plastiques entre grains voisins, y compris sous des confinements importants, représentatifs de la pression lithostatique de nombreuses cavités salines. L’augmentation de la pression de confinement et la présence de saumure semblent réduire le développement du réseau de microfissures. Ceci suggère que des mécanismes de dissolution et de précipitation pourraient être actifs et participer à l’accommodation des incompatibilités plastiques ou agir comme mécanisme de cicatrisation